1. Technical Field
The present disclosure relates to a nonaqueous electrolyte for a lithium secondary battery and a lithium secondary battery using the same, and more particularly, to a nonaqueous electrolyte for a lithium secondary battery exhibiting improved high-temperature storage characteristics at high voltage and a lithium secondary battery using the same.
2. Description of the Related Art
Batteries refer to apparatuses that convert chemical energy into electrical energy through electrochemical oxidation-reduction reactions of the chemical species in the batteries. Batteries are divided into primary batteries that are discarded when exhausted and secondary batteries that can be recharged and reused a plurality of times.
Conventional small and slim lithium secondary batteries used, for example, in mobile telephones, electronic organizers, and wrist watches include positive-electrode active materials comprising lithium-metal mixed oxides; negative-electrode active materials comprising carbon materials, lithium metal, and electrolytes comprising a lithium salt dissolved in an organic solvent.
To be specific, a typical electrolyte in a lithium secondary battery is obtained by dissolving LiPF6 in a mixture of a cyclic carbonic acid ether, such as propylene carbonate and/or ethylene carbonate, and an open-chain carbonic acid ether, such as dimethyl carbonate, methyl ethyl carbonate, and/or diethyl carbonate. Other organic solvents used in electrolytes include methyl ethyl carbonate (MEC) adopted in about 1993 and methyl propionate.
However, in order to improve the performances of batteries, in particular, high-temperature storage characteristics, specific compounds have been added to the electrolytes therefor. Typically, when specific compounds are added to the electrolyte in order to improve the performance of the battery, certain characteristics of the batteries are improved; however, other characteristics often are made worse. For example, some additives that improve high-temperature storage characteristics reduce the number of charging and discharging cycles possible for the battery.